System and method to monitor powerlines

ABSTRACT

The invention encompasses a system and method for monitoring a power line. In certain embodiments, a system emits a series of signals that allow for analytic analysis of a power line. For example, by taking multiple signal readings, it is possible to detect an average height reading of a power line and observe long-term trends in the time delay from signal emission to reception of an echo-signal. This allows for accurate measurement of various physical parameters of a power line, for example, the height of the power line above the ground.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.14/020,518 which was filed Sep. 6, 2013, which is allowed, and claimsthe benefit of U.S. provisional patent application No. 61/697,583, whichwas filed Sep. 6, 2012, the disclosures of each of which is incorporatedherein by reference in their entireties.

FIELD OF THE INVENTION

The invention encompasses a system and method for monitoring a powerline. In certain embodiments, a system emits a series of signals thatallow for analytic analysis of a power line. For example, by takingmultiple signal readings, it is possible to detect an average heightreading of a power line and observe long-term trends in the time delayfrom signal emission to reception of an echo-signal. This allows foraccurate measurement of various physical parameters of a power line, forexample, the height of the power line above the ground.

BACKGROUND OF THE INVENTION

High-voltage transmission power lines strung from support towers formthe backbone of the nation's electric power grid. Many of the powerlines supported by nearly the multitude of towers run through isolatedareas as they deliver electricity from generating plants to cities.

Continuous monitoring of electrical power lines, and in particular ofhigh-voltage overhead lines, is essential in order to timely detectanomalous conditions, which could lead to an outage. In some cases,monitoring allows avoiding the outage, for example, by reducing thepower transmitted by an overheated conductor while in other cases (e.g.,cable in a wind storm) a localized outage is unavoidable, but timelyintervention (e.g., by using monitoring information to redirect powerflow) can avoid its propagation through the power grid leading to ageneralized blackout.

Conventional approaches to monitor power lines can be time consuming,inaccurate, or require the actual presence of an engineer to physicallyconduct the measurement. For example, reflector-less laser technology isused for transmission and distribution applications such as sagprofiling, measuring the heights of attachment points or a conductorfrom the ground, verifying vegetation clearances and determining thelocation for your guy wire. However, this technique is limited in that aperson must stand at the location and measure the distance, height, andclearance values necessary to make critical decisions.

Other conventional methods use a time-domain reflectometer (TDR) tomeasure the change in impedance when a line is closer to the ground, butsuch a system does not provide very high accuracy as needed to predictpower line failure.

Therefore, it would be advantageous to provide a compact, lightweightsensing device that measures at least one characteristic of an overheadpower line that may be readily attached and removed from a power line.

SUMMARY OF THE INVENTION

The application generally encompasses systems and methods for monitoringa power line and in particular monitoring the height of a power linefrom the ground. The system and methods of the invention are much moreaccurate, use fewer resources, and do a better job of predicting powerline failure than conventional methods. The system and methods of theinvention also use far less power, and can be powered from scavengedpower, from a power line application, or from a solar cell array, forexample, from a cell phone.

In one embodiment, the invention encompasses a method for monitoring apower line comprising transmitting an identifiable signal from atransmitter device on a power line, receiving the signal from thetransmitter device on the power line by at least one sensor, processingthe received signal using data from the at least one sensor to identifya parameter of the power line, and reporting the parameter of the powerline to a network.

In certain embodiments, the frequency ranges from about 300 megahertz toabout 2 gigahertz.

In other embodiments, the frequency is in the range of about 800megahertz to about 900 megahertz.

In other embodiments, the frequency is in an acoustic range from 10 Hzto 1 MHz.

In other embodiments, the parameter is the distance of the power line ata given point along the power line from the ground.

In other embodiments, the transmitter device is a radio frequencytransmitter.

In other embodiments, the transmitter device is an audio frequencytransmitter.

In other embodiments, the transmitter device is a cell phone.

In other embodiments, the processing the received radio frequency signalis an arrival-time correlation process, distributed sensor/time offlight process, or an echolocation process.

In other embodiments, the processing of the received radio frequencysignal further comprises synchronizing using GPS.

In other embodiments, the system uses location services provided by GPS.

In other embodiments, the system uses location services provided by GSMor CDMA or systems like GOOGLE® location services.

In other embodiments, the parameter of the power line is reported usingwireless technology.

In other embodiments, the parameter of the power line is reported usingwireline modulation technology along the conductor span of the powerline.

In another embodiment, the invention encompasses a method fordetermining the height of a power line comprising receiving a radiofrequency signal from a source placed along a power line, processing areceived radio frequency signal using data received by a plurality ofsensors, identifying an approximate localized point on the power line,the approximate localized point defining a physical height of the powerline, and reporting the height of the power line over a network.

In another embodiment, the invention comprises a method for identifyinga physical parameter of a power line comprising contacting at least onetransmitting device with a power line, communicating informationregarding the power line from at least one transmitting device to one ormore receiving devices over a communication network; collecting with oneor more receiving devices objective data from the transmitting device,processing the objective data from the at least one transmitting deviceto identify certain physical parameters of the power line; wherein thephysical parameter comprises, for example, a distance from thetransmitting device to the ground to record height of a power line.

In certain embodiments, the transmitter device comprises at least one ofa GPS, a plurality of cell sites, a plurality of WiFi hotspots, and aplurality of other mobile devices.

In certain embodiments, the transmitting device is a radio-transmittingdevice.

In certain embodiments, the transmitting device is an audio-transmittingdevice.

In certain embodiments, the radio-transmitting device is a cell phone.

In certain embodiments, the transmitting device transmits a radiofrequency.

In certain embodiments, the radio frequency is in the range of about 300megahertz to about 2 gigahertz.

In certain embodiments, the radio frequency is in the range of about 800megahertz to about 900 megahertz.

In certain embodiments, the processing of the objective data receivedthrough a radio frequency signal is an arrival-time correlation process,distributed sensor/time of flight process, or an echolocation process.

In certain embodiments, the parameter of the power line is reportedusing wireless technology.

In another illustrative embodiment, a transmitter, for example a cellphone, is placed on a portion of each catenary on a power line,optionally in an orange ball to facilitate power line visibility. Thecell phone emits a chirp or pulse and performs echolocation as is knownin the art. By taking multiple readings, it is possible to average theheight reading and observe long-term trends in the time delay from chirpto received echo signal. This measures the height of the cell phoneabove the ground very accurately. If more than one point on a catenarywire height needs to be measured, multiple cell phones encased in orangeballs can be placed on the wire at different points along the catenary.

In still another illustrative embodiment, the cell phone measures theinstantaneous height above the ground through echolocation. In certainembodiments, the cell phone stores and periodically forwards themeasurements through the cellular data network to a central server orprocessing facility. In certain embodiments, the location processes thesignals, produces an annotated map with all the measurements and evenhistory of measurements, and signals any alarms as needed. In certainembodiments, the sag on a power line can be monitored as it isoccurring. In certain embodiments, the alarms can be set as needed forany deviation from normal operations.

In certain illustrative embodiments, software in the cell phone can dothe echolocation processing. It can also do timing, integrate GPSfunctionality, and manage data transmission to the central server.

In certain illustrative embodiments, in addition to measuring theecho-located height, a laser or optical or audio measurement couldprovide the height off the ground.

In certain illustrative embodiments, global positioning system (GPS) cansynchronize all the sensors and time their actuation. GPS can also beaveraged to get location down to centimeter resolution, for example, asis done for fault movement measurement in geology.

In another illustrative embodiment, GPS can synchronize two or moresystems and the time of flight can be measured between the two cellphones through the wire, thus measuring the impedance variation alongthe wire. Further, a round trip can be measured by transmitting alongthe wire from cell phone A to cell phone B, waiting a precise number ofnanoseconds, and return the signal back to the original phone. Then GPSclocks are not necessary, but simply a pair of precise timers, one tocount out a precise time delay from receipt to transmission, and theother to measure the amount of time elapsed from transmission toreception.

In certain embodiments, other sensing can be integrated, includingvibration, acceleration, noise, audio signals, local RF signals, lightlevels, images, videos and telemetering these to the central server.Commands can be received over the cellular or other wireless datanetwork. Power and signal can be conveyed on the powerlines themselvesas well.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an exemplary embodiment of the invention in whichtransmitters 111 are attached to power lines 101 wherein height andlength can be determined using echolocation and time of flightmeasurements synchronized by GPS.

FIG. 2 illustrates a close up of a transmitter 211 (illustrated as acircle) on a power line 201.

FIG. 3 illustrates another exemplary embodiment in which a transmitter311 (illustrated as a cell phone) emits a signal through a cellularnetwork to a receiver on a cell tower 331 and uses GPS and echolocationto determine the height of a power line 301.

FIG. 4 illustrates an exemplary schematic of the method of theinvention.

DETAILED DESCRIPTION OF THE INVENTION

The invention generally encompasses a system and method for monitoringpower lines. Such a monitoring device is provided with a housing whosedesign ensures a good electromagnetic shielding of the monitoringelectronics. This allows operating even in the harsh environmentconstituted by the vicinity of a high voltage (e.g., tens to hundreds ofkV) overhead power line. In certain embodiments, the transmitter deviceof the invention is capable of performing a complete monitoring of sag,vibrations, and movements of the power line. In certain exemplaryembodiments, the transmitting device of the invention is protectedagainst electromagnetic interferences, both quasi-static (low frequencyelectric and magnetic fields produced by normal operation of the line)and dynamical (transients due to commutations on the line, lightning,corona discharges) and despite being simple and lightweight, it allowsdetermining in real time-dependent physical parameters (e.g., height orsag) of the whole span of a power line.

In certain embodiments, the transmitting device of the inventionincludes a wireless connection device. As used herein, the term“wireless connection device” may be any device capable of achievingwireless connection between two or more electronic devices. In certainembodiments, a wireless connection device may be capable of beingwirelessly connected to one or more of the following electronic devices:wireless communication device, RFID devices, GPS devices, and the like,and/or combinations thereof, according to the particular application.

In certain embodiments, the transmitter device of the invention hasdimensions and an overall weight, which avoids an excessive perturbationof the mechanical properties of the monitored power line, which couldaffect the significance of the measurements. In certain exemplaryembodiments, the device is the size of a cellular phone. In otherembodiments, the device is a cellular phone.

In certain embodiments, the location of the transmitter device can becalculated using an onboard positioning information device that isincluded in the transmitting device, or by getting network-assistedposition information from the wireless network through a separate orsame wireless connection, such as, for example, Time-Of-Arrival (TOA)algorithm techniques.

In certain embodiments, the system may include a global positioningsystem device (referred to as GPS device). In certain illustrativeembodiments, the position information can also be obtained from acombination of a positioning information device, such as a GPS receiver,and a network-assisted approach, such as having the network sendephemeris data to the GPS receiver to help achieve faster time-to-fixtechniques.

As used herein, the term “GPS device” may be any device capable ofdetermining global position, according to the particular application.GPS device may be capable of communicating with a GPS satellite totransfer location information, such as coordinate location information,between a GPS device and one or more GPS satellites and/or aconstellation of satellites and/or space vehicles and/or groundequipment. A GPS device may be coupled to wireless communication deviceto be capable of communicating location and position information of apower line, such as coordinate location information, to a networksupport center.

In a certain embodiment, a GPS satellite may be in communication withguidance support center, so that the system of the invention may becapable of communicating positional information of a power line, such aspower line height and sag, to a network support center via GPSsatellite.

In another illustrative embodiment, the system may be capable ofcommunicating positional information, of a power line, to networksupport center via a radio frequency identification (RFID) device anddata communications system. The location information, such as power lineheight information, may be used by network support center for analysisof the integrity of a power line. The GPS device and/or GPS satellitecomprise one illustrative example of a location determining system forlocation system, and the scope of the claimed subject matter is notlimited in this respect.

In certain embodiments, the location information of the transmitterdevice can be provided by configuring the transmitter device to allowposition information to be received.

In certain embodiments, information regarding the location of thetransmitter device is sent to the wireless network via a directconnection. The wireless network is connected to the wireless device aby means of a wireless connection, such as a radio frequency (RF),optical, or infrared connection, using various connection standards,such as CDMA, GSM, GPRS, WCDMA, or CDMA2000. In one illustrativeembodiment, the information sent from the transmitter device containsthe originating position and transmitter identification information,since the local position information is already known. In anotherembodiment, the information is sent directly to the wireless networkthrough a dedicated connection.

In another embodiment, the transmitter device continually sends updatedlocational information to a receiving device, for example, on a cellularnetwork tower. This continual signal providing real-time locationinformation that allows a network operator to display and identifyreal-time positions of the transmitting device on a map of varyingresolution and to determine changes in position, for example, a downedor sagging power line. In this embodiment, this positional informationexchange is determined by a network operator.

In another embodiment, the position location information of thetransmitter device is transferred to the wireless network by means of awireless connection. The position information is calculated, prior tothe transfer, by means of an onboard positioning information device thatis connected to the transmitter device, or by receiving positioninformation from the wireless network using a network assistedpositioning approach. In certain embodiments, the receiving sensordevice receives the position information for all the transmittingdevices in real time.

In one embodiment, the information from the transmitter device isrelayed to the receiver device through the wireless connection into thewireless network and through a dedicated server connection.

In another embodiment, the information from the transmitting device isrelayed to the receiver device through a wireless connection into thewireless network or through a dedicated connection into the Internet,Intranet or Extranet.

In another embodiment, the receiving device requests positionalinformation from the transmitting device attached to the power line.This request, after reaching the wireless network, is sent across thewireless connection to the transmitting device.

In certain embodiments, the transmitter device forwards its currentpositional information back to the receiving device. The transmittingdevices, which are located at intervals along the power linescontinually send their positional information to the plurality ofreceiving devices. In certain embodiments, an alarm is triggered whenthe position information has changed significantly as compared to thepositioning error probability and as determined by the positioningtechnology or network configuration.

In certain embodiments, the network periodically updates eachtransmitting device with the other's positional information, thusproviding real-time locational and position information. For example, ifthe power line changes by a certain height, for example, by greater than3 cm, greater than 5 cm, greater than 10 cm, greater than 15 cm, greaterthan 20 cm, greater than 30 cm, greater than 50 cm, greater than 75 cm,greater than 100 cm, or greater than 500 cm this is an indication thatpower line may be experiencing sag or breakage and may require physicalinspection or repair.

In certain other embodiments, when a transmitting device's positioninformation is requested by a network administrator, the system respondswith the appropriate position by transmitting information from atransmitting device to one or more receiving devices through thewireless network.

In certain embodiments, using information received from a transmittingdevice, it is possible to obtain the local position and any change inposition for the purpose of monitoring a power line.

An exemplary system of the invention contains a processor, a pluralityof transmitting devices equipped with a position determining systemsituated along one or more power lines, a memory or storage device, aplurality of receiving devices, a user interface, and a display. Incertain embodiments, a user interface and display are combined and arelocated at a network hub, for example a power station. Once thepositional information has been obtained, as previously described, thesystem can utilize this position information to provide certaininformation on the integrity of a power line.

In another embodiment, the system of the invention calculates all of thepositional information and passes the information over to anotherdevice, such as a mobile computer, via a compatible connection interfacein order to better display the information. As the transmitting devicechanges its position, position and/or data information is sent to thereceiving device, via the cell network for real-time accurate dataupdates on the power line.

In another embodiment, a transmitting device of the invention contains,for example, a PDA, cellular telephone, or mobile computer, which haswireless connectivity. In this embodiment, the transmitting device canobtain position information by connecting through the wirelessconnection to the wireless network interface, which is then connected tothe Internet, Intranet or Extranet, which is then connected to thenetwork administrator.

In another embodiment, the transmitting device calculatesinstantaneously and continually a start position and a finish positionof a power line. The transmitting device then sends, or pushes, thisrelational data to a receiving device. This insures that the data forpower line position information is always up-to-date, reliable, andaccurate.

In certain embodiments, the transmitter device includes hardware andfurther includes a transmitter and a receiver. The implementation of atransmitter enables additional positional location of the transmitter(and accordingly the power line) to be determined using ultrasonic oraudio or infrasound echolocation. An embodiment of the transmitter thatimplements emitters and receivers would be configured with appropriateexterior features to enable proper function of the emitters andreceivers.

In certain embodiments of the invention, there is included in thetransmitter device an echolocation system. Also included in thetransmitter device are transmitter circuits and a transmitter, receiversand corresponding receiver circuits.

In certain embodiments, the transmitter circuits comprise a variablefrequency oscillator (VFO), a digital frequency synthesizer (DFS), and adigital signal processor (DSP). The variable frequency oscillatorgenerates an acoustic pulse at a frequency controlled by the digitalfrequency synthesizer. The acoustic pulse is then formatted in thedesired signal configurations by the digital signal processor.

The system of the invention in certain illustrative embodiments may alsoinclude a radio frequency identification device (referred to as RFIDdevice hereinafter).

As used herein, the term “RFID device” may be any device capable oftransferring radio frequency identification information. Examples ofRFID devices may include, but are not limited to active RFID devices,passive RFID devices, the like, and/or combinations thereof, accordingto the particular application. RFID device may be capable ofcommunicating with a second RFID device located adjacent or remote fromsystem to transfer RFID information between a first RFID device and asecond RFID device. For example, an RFID device may include an RFIDreader and/or an RFID tag, where RFID reader of RFID device may retrieveRFID information from an RFID tag of RFID device and/or where RFID tagof RFID device may deliver RFID information to RFID reader of RFIDdevice. An exemplary RFID device may be coupled to wirelesscommunication device to be capable of communicating locationinformation, such as RFID information, to a network support center viawireless communication network.

In certain embodiments, a data communications system may be incommunication with RFID device as well as the network support center, sothat the system may be capable of communicating location and positioninformation, such as RFID information, to guidance support center viaRFID device and data communications system.

In certain embodiments, the system may be capable of communicatinglocation information or position information of a power line to anetwork support center via RFID device and data communications system.

In certain embodiments, the power system may be scavenged from the powerline conductors using passive or active electrical circuits andelectrodes placed at advantageous locations in, on or near the powerlinesensor. These circuits may comprise one or more electrodes, capacitors,diodes, switched capacitor circuits or photovoltaic arrays, among otherelectronic components.

As used herein, the term “data communications system” may be any systemcapable of data communications. Examples of data communications systemsmay include, but are not limited to online Network Operations Center(hereinafter NOC), and/or the like, according to the particularapplication. The location information, such as RFID information, may beused by network support center for analysis of location and positiondata to monitor the integrity of a power line. The RFID device comprisesone illustrative example of a position determining system of theinvention, and the scope of the claimed subject matter is not limited inthis respect.

In certain embodiments, the system may include a camera. As used herein,the term “camera” may be any device capable of processing visuallocation information, including but not limited to picture information,video information, the like, and/or combinations thereof, according tothe particular application. A camera may be coupled to wirelesscommunication device to be capable of communicating locationinformation, such as power line height, to a network support center. Incertain embodiments, a system may be capable of communicating positionalinformation, such as power line height information, to network supportcenter via a RFID device and data communications system.

In certain embodiments, a database may be connected to network supportcenter. A database may communicate with network support center to supplyadditional information to network support center. As used herein, theterm “additional information” may include, but is not limited to dataand/or programs including, but not limited to: public and/or privatemapping information, address information, transmitter distances,transmitter height, the like, and/or combinations thereof.

Examples

A non-limiting exemplary power line monitoring system according to theinvention comprises a plurality of transmitting devices located on spansof a power line and a plurality of receiving devices for collection andprocessing, in which the transmitting devices send information to aseries of receiving devices using a cellular network.

If the transmitting devices are directly connected to a suitabletelecommunication system such as a cellular network, the remote stationscan be dispensed for measurement data being transmitted to the centralstation through a telecommunication system. Optionally, it isadvantageous that transmitting devices comprise a pre-processor in orderto compress raw measurement data before transmitting them. In theextreme compression case, data is reported only when it exceeds anacceptable range. Heartbeat communication signals ensure that the systemis active and functioning properly.

Transmitted data are processed at the remote station in order to convertraw measurement data into directly exploitable monitoring information;it will be understood that transmitting devices can comprise a dataprocessor in order to perform in situ pre-processing of said measurementdata. The location of the transmitting device is typically calculated bythe transmitting device by using an onboard positioning informationdevice that is connected to the transmitting device, or by gettingnetwork-assisted position information from the wireless network througha separate or same wireless connection, such as, for example,Time-Of-Arrival (TOA) algorithm techniques. The position information canalso be obtained from a combination of an onboard positioninginformation device, such as a GPS receiver, and a network-assistedapproach, such as having the network send ephemeris data to the GPSreceiver to help achieve faster time-to-fix techniques. The transmittingdevice can further use echolocation to determine certain other data, forexample, distance between transmitting devices or height of thetransmitting device from the ground below said transmitting device.

It should be noted that the present invention may be embodied in formsother than the preferred embodiments described above without departingfrom the spirit or essential characteristics thereof. The specificationcontained herein provides sufficient disclosure for one skilled in theart to implement the various embodiments of the present invention,including the preferred embodiment, which should be considered in allaspect as illustrative and not restrictive; all changes or alternativesthat fall within the meaning and range or equivalency of the claim areintended to be embraced within.

1. A method for monitoring a power line comprising: a. transmitting anidentifiable signal from a transmitter device defined on a power line;b. receiving the signal from the transmitter device defined on the powerline by at least one receiving device; c. processing the received signalusing data from the at least one receiving device to identify aparameter of the power line; and d. reporting the parameter of the powerline to a network, wherein a database communicates with the networksupport center to supply information including mapping information ofthe transmitter device, address information of the transmitter device,transmitter distances, and transmitter height.
 2. The method of claim 1,wherein the signal is a radio frequency signal in the range of about 300megahertz to about 2 gigahertz.
 3. The method of claim 1, wherein thesignal is a radio frequency signal in the range of about 800 megahertzto about 900 megahertz.
 4. The method of claim 1, wherein the parameteris the distance of the power line at a given point along the power linefrom the ground.
 5. The method of claim 1, wherein the transmitterdevice is a radio frequency transmitter.
 6. The method of claim 1,wherein the transmitter device is an audio frequency transmitter.
 7. Themethod of claim 1, wherein the transmitter device is a cell phone. 8.The method as recited in claim 1, wherein the processing the receivedradio frequency signal is an arrival-time correlation process,distributed sensor/time of flight process, or an echolocation process.9. The method as recited in claim 1, wherein the processing the receivedradio frequency signal further comprises synchronizing using a globalpositioning system (GPS).
 10. The method of claim 1, wherein theparameter of the power line is reported using wireless technology.
 11. Amethod for determining the height of a power line comprising: a.receiving a radio frequency signal from a source placed on a power line;b. processing the received radio frequency signal using a plurality ofreceiving devices; c. identifying an approximate localized point on thepower line, the approximate localized point defining a physical heightof the power line; and d. reporting the height of the power line over anetwork to a network operator, wherein a database communicates with thenetwork support center to supply information including mappinginformation of the transmitter device, address information of thetransmitter device, transmitter distances, and transmitter height.
 12. Amethod for determining the height of a power line comprising: a.receiving a signal from a source placed on a power line; b. processingthe received signal using a receiving device; c. identifying anapproximate localized point on the power line, the approximate localizedpoint including a physical height of the power line; and d. reportingthe height of the power line over a network to a network operator,wherein a database communicates with the network support center tosupply information including mapping information of the transmitterdevice, address information of the transmitter device, transmitterdistances, and transmitter height.
 13. A method for identifying aphysical parameter of a power line comprising: a. contacting at leastone transmitting device to the power line; b. communicating a signalfrom the at least one transmitting device to a plurality of receivingdevices over a communication network; c. processing the signal using aprocessor to identify at least one physical parameter of thetransmitting device on the power line; d. collecting data with regard tothe physical parameter of the transmitting device, e. reporting thephysical parameter to a network operator, wherein a databasecommunicates with the network support center to supply informationincluding mapping information of the transmitter device, addressinformation of the transmitter device, transmitter distances, andtransmitter height.
 14. The method of claim 11, wherein the receiving ofa radio frequency is achieved through at least one of a GPS, a pluralityof cell sites, a plurality of WiFi hotspots, and a plurality of othermobile devices.
 15. The method of claim 11, wherein the source is atransmitting device comprising a radio-transmitting device.
 16. Themethod of claim 15, wherein the radio-transmitting device is a cellphone.
 17. The method of claim 15, wherein the transmitting devicetransmits a radio frequency.
 18. The method of claim 15, wherein thesource transmits a radio frequency in the range of about 600 megahertzto about 2 gigahertz.
 19. The method of claim 15, wherein the sourcetransmits a radio frequency in the range of about 800 megahertz to about900 megahertz.
 20. The method as recited in claim 11, wherein theprocessing the received radio frequency signal is an arrival-timecorrelation process, distributed sensor/time of flight process, or anecholocation process.
 21. The method of claim 1, wherein the parameterof the power line is reported using wireless technology.